1. Field of the Invention
The present invention relates to the field of fire extinguishing compositions and methods using halogenated hydrocarbons.
2. Description of the Prior Art
The use of certain halogenated chemical agents for the extinguishment of fires is common. These agents are thought to be effective due to their interference with the normal chain reactions responsible for flame propagation. The most widely accepted mechanism for flame suppression is the radical trap mechanism proposed by Fryburg in Review of Literature Pertinent to Fire Extinguishing Agents and to Basic Mechanisms Involved in Their Action, NACA-TN 2102 (1950). It is generally accepted that compounds containing the halogens Cl, Br and I act by interfering with free radical or ionic species in the flame, and that the effectiveness of these halogens is in the order I&gt;Br&gt;Cl. The presence of fluorine has not been considered as contributing to the fire extinguishing properties of a compound, but will impart stability, reduce toxicity and boiling point and increase thermal stability.
Various halogenated hydrocarbons have been used or proposed for use as fire extinguishants. Prior to 1945, three halogenated fire extinguishing agents widely used were carbon tetrachloride (Halon 104), methyl bromide (Halon 1001) and chlorobromomethane (Halon 1011). For toxicological reasons, however, the use of these agents has been discontinued. The three fire extinguishing agents presently in common use are bromine-containing compounds, Halon 1301 (CF.sub.3 Br), Halon 1211 (CF.sub.2 BrCl) and Halon 2402 (CF.sub.2 BrCF.sub.2 Br). The effectiveness of these three volatile, bromine-containing compounds in extinguishing fires has been described in U.S. Pat. No. 4,014,799, issued to Owens. In addition, the use of dibromodifluoromethane, Halon 1202 (CF.sub.2 Br.sub.2), has been reported, although the compound is highly toxic. The NFPA publication, the Fire Protection Handbook, Section 18, Chapter 2, entitled "Halogenated Agents and Systems" (1985) describes these agents in more detail.
Although the above named bromine-containing Halons are effective fire fighting agents, those agents containing bromine or chlorine are asserted by some to be capable of the destruction of the earth's protective ozone layer. For example, Halon 1301 has an Ozone Depletion Potential (ODP) rating of 14.26, and Halon 1211 has an ODP of 2.64. Also, because the agents contain no hydrogen atoms which would permit their destruction in the troposphere, the agents may also contribute to the greenhouse warming effect.
Although not employed commercially, certain chlorine-containing compounds are also known to be effective extinguishing agents, for example Halon 251 (CF.sub.3 CF.sub.2 Cl), as described by Larsen in U.S. Pat. No. 3,844,354. The use of trichlorofluoromethane (CFCl.sub.3) with all or any of dichlorodifluoromethane (CCl.sub.2 F.sub.2), trichlorotrifluoroethane (CCl.sub.2 F-CClF.sub.2) or dichlorotetrafluoroethane (CClF.sub.2 -CClF.sub.2) in fire extinguishers is disclosed in U.S. Pat. No. 4,826,610, issued to Thacker on May 2, 1989. In U.S. Pat. No. 3,733,273, issued to Munro on May 15, 1973, it is disclosed that an azeotropic mixture of 1,2-dichloro-1,1,2,2-tetrafluoroethane and 1-chloro-1,2,2-trifluoroethane is useful as a fire extinguishing agent. Various other halogenated fire extinguishing agents have been disclosed in the prior art, including in U.S. Pat. Nos. 4,606,832, issued to Hisamoto et al. on Aug. 19, 1986; 3,879,297, issued to Languille et al. on Apr. 22, 1975; 3,822,207, issued to Howard et al. on Jul. 2, 1974; 3,080,430, issued to Cohen on Mar. 5, 1963; and, 4,226,728, issued to Kung on Oct. 7, 1980.
Several factors enter into the selection and use of halogenated hydrocarbons as fire extinguishants. As already mentioned, brominated hydrocarbons in particular present concerns with ozone depletion. Compounds which do not include bromine tend to be ineffective at safe levels, or toxic at effective levels. It has therefore remained desirable to provide fire extinguishants which satisfy the various criteria applicable for use of these compounds. In particular, there continues to be a need for fire extinguishing agents which are effective and non-toxic, and which have low ozone depletion ratings and minimal impact on the greenhouse warming effect.
The present invention involves the use of 2-Chloro-1,1,1,2-tetrafluoroethane as a fire extinguishant, either alone or in combination with other compounds. This compound is commonly known as Freon 124. Applicant has discovered that this compound has surprising efficacy at safe concentrations. Although the compound is well known, it has not been proposed for use as a fire extinguishant. Instead, Freon 124 has only been indicated in the past as being useful as a propellant or refrigerant.